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Issue 17, 2011
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An abinitio study of electrochemical vs. electromechanical properties: the case of CO adsorbed on a Pt(111) surface

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Abstract

We have studied electrochemical vibrational and energy properties of CO/Pt(111) in the framework of periodic density functional theory (DFT) calculations. We have used a modified version of the previously developed Filhol–Neurock method to correct the unphysical contributions arising from homogeneous background countercharge in the case of thick metallic slabs. The stability of different CO adsorption sites on Pt(111) (Top, Bridge, Hcp, Fcc) has been studied at constant electric field. The energies are dominated by the surface dipole interaction with the external electric field: a strong positive electric field favors the surfaces with the lower dipole moment (that correspond to the ones with the lower coordination). The Stark tuning slope of the CO stretching frequency for a Top site was calculated for different surface coverages in very good agreement with both experimental and other theoretical results. Finally, we have performed an analysis of the origin of Stark shifts showing that the total Stark effect can be split into two competing components. The first one corresponds to the direct effect of charging on the C–O chemical bond: it is referred as an electrochemical effect. The second is the consequence of the surface dipole interaction with the applied electric field that modifies the C–O distance, inducing a change of the C–O force constant because of C–O bond anharmonicity: it is referred as the electromechanical effect. In the CO/Pt(111) case, the dominant contribution is electromechanical. The electrochemical contribution is very small because the electronic system involved in the surface charging is mostly non-bonding as analyzed by looking at the surface Fukui function.

Graphical abstract: An abinitio study of electrochemical vs. electromechanical properties: the case of CO adsorbed on a Pt(111) surface

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Publication details

The article was received on 06 Aug 2010, accepted on 21 Jan 2011 and first published on 15 Feb 2011


Article type: Paper
DOI: 10.1039/C0CP01444C
Citation: Phys. Chem. Chem. Phys., 2011,13, 7675-7684

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    An abinitio study of electrochemical vs. electromechanical properties: the case of CO adsorbed on a Pt(111) surface

    M. Mamatkulov and J.-S. Filhol, Phys. Chem. Chem. Phys., 2011, 13, 7675
    DOI: 10.1039/C0CP01444C

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